In a current wireless communication environment, the amount of data necessary for a communication network is rapidly increasing due to Machine-to-Machine (M2M) communication and the appearance and spread of a variety of devices, such as smart phones and tablet PCs which require a large amount of transmission data. In order to satisfy a large amount of transmission data, communication technology is being developed into carrier aggregation technology for efficiently using a greater frequency band, cognitive radio technology, multi-antenna technology for increasing the capacity of data within a limited frequency, multi-base station cooperation technology, and so on.
Furthermore, a wireless communication environment is evolving into an increase in the density of nodes which may access user peripheries. Here, the nodes refer to antennas or a group of antennas which are spaced apart from one another at specific intervals or higher in a Distributed Antenna System (DAS). In the present invention, however, the nodes are not limited to the above meaning, but may be used in a broad sense. The node may be a base station, a picocell base station (PeNB), a home base station (HeNB), a Remote Radio Head (RRH), a Remote Radio Unit (RRU), a relay station, a distributed antenna, or the like. A wireless communication system having a high density of nodes may show higher system performance through cooperation between the nodes. That is, each node operates as an independent Base Station (BS) (or Advanced BS (ABS), Node-B (NB), eNode-B (eNB), or Access Point (AP), etc.) and thus has much excellent system performance as compared with the case when they do not cooperate with each other.
FIG. 1 shows an example of a multi-node system.
Referring to FIG. 1, the multi-node system includes a plurality of nodes. In FIG. 1, a node indicated by an antenna node may be a BS, a picocell BS (PeNB), a hone BS (HeNB), a Remote Radio Head (RRH), a relay station, or a distributed antenna. This node is also called a point.
In a multi-node system, if the transmission and reception of all nodes are managed by one BS controller and thus an individual node operates as part of one cell, this system may be called a Distributed Antenna System (DAS) that forms one cell. In a DAS, all nodes may be given respective node IDs, and they may operate as a set of some antennas within a cell without separate node IDs. In other words, a Distributed Antenna System (DAS) means a system in which antennas are distributed over and disposed at various positions within a cell and the antennas are managed by a BS. A DAS differs from a conventional Centralized Antenna System (CAS) in that the antennas of a BS are concentrated on the center of a cell and disposed.
In a multi-node system, if an individual node has an individual cell ID and performs scheduling and handover, this system may be considered as a multi-cell (e.g., macrocell/femtocell/picocell) system. If multi-cells are configured in such a way as to overlap with each other according to coverage, this is called a multi-tier network.
In a multi-node system, such as a distributed antenna system or a multi-tier network, nodes that transmit signals to respective terminals may be different, and nodes that receive signals from terminals may be different. Accordingly, if a terminal feeds back information on a channel state using a method as in a CAS, there is a problem in that a BS does not know that the information is feedback information on what node.
There is a need for a method and apparatus for transmitting feedback information of a terminal in a multi-node system.